I think the only limiting factor will be height if you have large strains as you would need around 8" for the pot and between 16-24" for the lighting distance/ hangers and space for filter if it intrudes, your only left with two foot for the plants. Id kill for more sizing options. 5x2.5x6 tent would be amazing for 3 autos, as I find 4x2x5 a bit of a struggle with three plants, but if your on top of your training, have enough light that stretch is negated you should be fine. The closest I've found is the spider farmer 140x70x200 tents, but they are three times the price of anything else here.
Keep in mind I could be full of shit. This is coming from my circle of amateur growers in a hot climate, and my current experience with autos in 60x60 and 100x50 tents. There should be someone with far more experience coming along soon that have had far better results than me and a few mates with limited environmental control or experience.